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Upgrading to MkIII Injection

The following question, also emailed by Richard Fairclough, produced such a detailed answer from Ken that it has warranted a whole section of its own.


Q: Could you give me the key points and a brief outline of what's involved in upgrading to Mk III injection spec?

A: That's asking a bit, because it's not exactly a simple job, but here goes. Please note that because this exposition is necessarily relatively brief, it's by no means exhaustive. For more detailed information, navigate to the Roger Parker article on which (with his kind permission) the following is based:

Frontline Costello does not supply the majority of the parts for the Mk III EFI conversion, so a complete Rover system needs to be sourced. Having tried both types, I would rule out the earlier airflow meter system and opt for the hot wire system as a more modern and accurate approach to fuel management. This system was fitted to all Land Rover V8 engines from 1989 (1988 for US models) to 1995 (ish). The first V8 engine to use this system was the Range Rover 3.9, closely followed by the 3.5 in the Discovery. Later on there would be a 4.2 litre version in Range Rover LSE. This is also the version that TVR used to good effect with other engine capacities, together with re-mapped ECUs to match them.


Fuel Flow

The injection system requires a constant, clean, high-pressure, high-volume fuel feed to work properly. This is done by having a supply that is not subject to air pick up even when fuel tank levels are low. In most production cars, internal baffles fitted in the fuel tank to prevent surge achieve this - alternatively, what is known as a swirl pot is built into the inner base of the tank. The latter is what is used in the RV8 and in the long-range aluminium fuel tank from Frontline Costello.

The pump is special too, as it delivers up to 4.1 bar pressure (60psi) along with a huge volume. In this application the pump is mounted outside the tank at or very near its base line. To cope with the volume, the tank to pump feed ideally needs to be 12.8mm (1/2") bore. However, the RV8 went against all previous fits in using a modified MGB rubber bumper sender/fuel pick up with a 1/4" bore pipe into the tank before opening out to 1/2" bore via a one-off hose right at the pump inlet. Though not 'by the book', this works well enough, so the simplest way forward is to use RV8 parts, especially the tank. Similar (Bosch usually) pumps are found on a large number of other cars from many manufacturers, but not all have the required performance parameters. Suitable aftermarket fuel pumps are offered by companies like Sytec and Walbro.

The fuel is fed at high pressure to the engine, via the fuel rail and injectors. It is a good idea to have the injectors cleaned and tested by a specialist before re-using them. At the end of the fuel rail is a pressure regulator that maintains fuel at a predetermined pressure above that which is found in the inlet manifold. This is usually a base 2.5 bar (36psi) for the V8, dropping to around 1.8 bar (28psi) through the manifold vacuum connection when the engine is running with a closed throttle. The excess fuel bled off by the pressure regulator is routed back to the swirl pot in the tank via a second fuel return line. The fitting of a suitable in-line filter between fuel pump and injectors is vital.


Air Flow

Air enters the air filter as in any other engine. The hot wire system then measures the volume and temperature with the information being passed to the ECU. The air progresses through to the throttle housing on the plenum inlet where the rate of flow is controlled by the throttle disc in the same way as in a normal engine. On the end of the throttle spindle is a variable potentiometer that provides different voltage levels to the ECU, showing the position, direction and degree of movement of the throttle. Idle speed is controlled via a variable air bleed which allows filtered and measured air to bypass the throttle. Depending on the system, this can be controlled via the ECU.

Overall airflow for larger capacity engines can be increased by having the standard 65mm throttle body bored out, or by replacing it with an aftermarket (usually American) substitute of up to 100mm in bore diameter. There are other alternatives - using two or three standard throttle bodies in tandem on one plenum, for example - but they are not Costello developed components and I have no experience of them. Beyond that is the fully approved Wildcat eight-port system, but this can only be used in conjunction with the company's own design of cylinder heads.



The ECU controls the whole of the system. It receives engine speed information from a connection to the negative side of the coil, throttle position information from the throttle potentiometer, and airflow information from the hot wire meter. Additional information comes from the coolant sensor, air temperature sensor, and depending on system, inputs from a number of other possible sources. Standard ECUs can be remapped to suit more highly tuned engines, but eventually only an aftermarket unit from the likes of Emerald or Omex will suffice.


Fitting the Injection

The one big advantage with the V8 injection systems is the fact that they are contained mostly within the inlet manifold assembly. This means that any Rover V8, and probably its GM forerunners too, can have injection applied to them. To confirm whether any non-Rover engine could be fitted, a general guide is to check whether the injection inlet manifold from a Rover V8 will fit the subject engine - if so, then so will injection.


In an MGB, the standard Rover plenum chamber creates under-bonnet clearance problems and the intake is not ideally placed. The Costello plenum is lower and has the inlet to the rear, where the hot wire meter/throttle body simply bolts on, together with a conical air cleaner from, say, ITG or K & N. Costello plenums are still available to special order. Fitting requires machining approximately 20mm off the bottom of the original plenum casting which houses the steel ram pipes (and matching it to the manifold underneath). Next, the standard 38mm ram pipes are shortened to give adequate clearance between them and the underside of the plenum top, whilst retaining the differential between the centre and outer ram pipes - or replacing them with suitable alloy or carbon fibre after-market items. These are available in larger bore diameters - 45mm is a popular alternative - for tuned or bigger capacity engines. Machining the bottom of the plenum casting, as above, should not be necessary if an original Costello bonnet is fitted.


The Rover injection wiring is fairly user friendly as it is restricted to a separate sub-loom with just a handful of connections to go to the car - the number and functions varying slightly depending on system and age. The ECU and other relays etc. are best mounted in the passenger area as this provides a more stable environment. The underside of the dash above the passenger foot well was a favourite choice. It was also found useful to have a separate power feed from the starter solenoid to a dedicated fuse box, from which the engine management and other additional functions could be added without the need to overload the original and basic systems.

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